Age at menarche in Iran

Background: Age at menarche and its potential associated factors are reported for 1862 Shiraz (Southern Iran) secondary school girls taking part in a cross-sectional survey selected from the four educational districts of the city. Methods: Probit analysis was used to estimate age at menarche, principal component analysis (PCA) was applied to analyse socio-economic status (SES). Body mass index (BMI) was used as an indicator of nutrition. Results: Mean+/-SD age at menarche was 12.91+/-1.23 years (95% CI: 12.84-12.97). Of all subjects, 33.7% first menstruated in summer. The highest mean age at menarche was 13.01 years in winter. Stress, anxiety and discomfort was seen among 70.3% of subjects at menarche indicating total or partial ignorance of the menstruation phenomenon. Age at menarche decreased as SES improved. Menarcheal age was delayed for underweight subjects. Conclusions: It is concluded that BMI and SES had the most significant effects on variation of menarcheal age in a unified statistical model. However, their interaction was found to be not statistically significant.